The present invention relates to a hollow body product, such as a hollow body product in which a fiber-reinforced resin plate having a concave part and a flat fiber-reinforced resin plate are bonded together and integrated.
A hollow body product such as a pipe can be formed by using a core made of metal or rubber.
However, some types of hollow body product, such as the one used for a landing gear door of an aircraft (see FIG. 3 (plan view) and FIG. 4 (A-A cross-sectional view)) cannot be formed by the method using a core since the core which has been used cannot be taken out.
Nevertheless, even hollow body products like the one shown in FIGS. 3 and 4 can be formed by the method if the core is made of a water-soluble material. This is because the core can be discharged from the hollow part of the product by supplying water to the inside of the hollow part through a hole connecting to the hollow part and causing the core to be dissolved in the supplied water. However, the core is necessary even in this case and the production cost is necessitated to increase correspondingly.